"Improbable Cause" is the 66th episode of the television series Star Trek: Deep Space Nine, the 20th episode of the third season. It is the first half of a two-part episode, concluded in the following episode, "The Die is Cast". Set in the 24th century, the series follows the adventures of the crew of the space station Deep Space Nine near the planet Bajor, adjacent to a wormhole connecting the Alpha and Gamma Quadrants of the galaxy, as the Bajorans recover from a decades-long occupation by the imperialistic Cardassians. The Gamma Quadrant is home to a hostile empire known as the Dominion, ruled by the shapeshifting Founders. In this episode, Deep Space Nine's security chief Odo investigates a bombing at the clothing shop of Cardassian spy-turned-tailor Elim Garak, leading him to discover secret Cardassian maneuvering against the Dominion. Plot When Garak's shop explodes, Odo finds that it was destroyed by a bomb set up to make it look accidental. He tracks down a possible suspect but before he can catch up with him, the suspect is killed when his ship blows up. Odo studies the case further and discovers evidence that the Romulans, a rival alien race, are behind it. They probably hired the dead suspect, and then killed him to help bury evidence. Odo digs up more information about the incident and finds that it is much more complicated than an assassination attempt on Garak. It seems the Romulans are planning to invade Cardassia and several members of the Obsidian Order, the Cardassian secret police, have been killed in mysterious mishaps recently. Odo tries to get Garak to admit that he blew up his own shop in order to get Odo to begin an investigation. All of the Cardassians recently killed were close to Enabran Tain, Garak's Obsidian Order mentor. Now that all of his associates are being targeted, Tain may be in danger. Odo and Garak set off to locate him. En route they are captured by a Romulan starship. When they are brought aboard they find Tain is there. He tells them he ordered Garak's assassination, as well as those of the rest of his former associates. He is wiping his history clean in preparation for a power play. The Tal Shiar, the Romulan intelligence agency, have formed an alliance with the Obsidian Order, and they are planning an attack on the Founders in the Gamma Quadrant.